The present invention relates to testing equipment for internal combustion engines. In particular, the present invention relates to a test probe clip adapted to clip on ignition wires.
As technology in the area of automotive systems has advanced, automotive test apparatus has followed and become increasingly more sophisticated. Present day automotive engine analyzer equipment requires many electrical connections to the engine under test. The connections are typically made with a pick-up or probe that clips onto an engine wire. The pick-ups use direct electrical contact along with capacitive and inductive coupling. For example, to measure battery voltage a direct electrical connection can be made to the automotive battery. In signals where AC components are present, the engine analyzer can be capacitively or inductively coupled to the signal through a test probe.
In an inductively coupled test probe, a testing coil is placed around a signal wire to be tested, an ignition wire for example The AC components present in the signal wire are inductively transferred to the testing coil The testing coil is connected to an amplifier for amplifying weak signals from the testing coil A capacitive test probe functions in a similar manner except that a capacitive probe uses a capacitor plate rather than an inductive coil as a signal pick-up. Signals from the capacitive test probe are amplified for use with the engine analyzer circuitry. In either case, electrical signals are provided which represent the AC components in the signal wire under test, without direct electrical connection to the engine wire.
In traditional ignition systems having a distributor and an ignition coil, the secondary voltage (which causes the spark plugs to fire) is sensed with a single high tension probe clamped over the secondary wire between the ignition coil and the center terminal of the distributor. In distributorless ignition system (DIS) on the other hand, there is no distributor and no single wire which carries the secondary voltage for all spark plugs. To sense secondary voltages in a DIS engine, an inductive or capacitive sensor must be connected over spark plug wires of the engine under test.
The probe clip used to connect the engine analyzer equipment to the spark plug wires of a DIS engine under test is of critical importance. If the clip does not remain in proper contact with the spark plug wires, the engine analyzer cannot provide accurate test results. A typical probe clip uses a resilient plastic material adapted to fit over the spark plug wire. The ignition wire is forced into the clip and the spring action of the clip material retains the wire. Unfortunately, spark plug wires vary in diameter. A probe clip adapted for a large diameter ignition wire cannot be securely clipped to a small diameter ignition wire. On the other hand, a probe clip adapted for a small diameter ignition wire tends to stretch out of shape when used with large diameter wires.
An inexpensive test probe clip for an engine analyzer system adapted for receiving both large and small diameter spark plug wires without being damaged would be a significant contribution to the art.